Comparison of crystal and solution structures and 1H and 13C chemical shifts for grandiflorenic acid, kaurenoic acid, and monoginoic acid

Abstract

The crystal structure of monoginoic acid, 3, is determined and compared with previously reported structures of kauradienoic acid, 1, and kaurenoic acid, 2. 1H and 13C chemical shifts are assigned for all three diterpenes and solution and crystal structure conformations are confirmed with the aid of solution NOE measurements. The overall shapes of 2 and 3 are very similar while 1 is significantly dissimilar. These differences may be partially responsible for the reported greater in vitro uterotropic activity of 1, relative to 2 and 3. Keywords: monoginoic acid, kaurodienoic acid, kaurenoic acid.